U.S. Military leaders are prepared to back Afghan President Hamid Karzai's timeline for U.S. troop withdrawal, saying in roundtable meeting with reporters Monday that Afghan security forces should be able to handle the country's security on their own by 2014.

Defense Secretary Robert Gates said the withdrawal timeline will discussed further at an upcoming NATO summit in Lisbon, Portugal at the end of the month.

"One of the agenda items for the Lisbon summit is to embrace president Karzai's goal of completing the transfer of security responsibility to Afghanistan by 2014," the Pentagon chief said.

Lt. Gen. William Caldwell, head of NATO's training mission in Afghanistan, says he'll need around 900 more trainers to get the Afghan forces ready in time. That's roughly half of what he's working with now and without them, Caldwell says, the goal won't be met.

Critics say that by announcing this need for additional trainers two weeks before the NATO summit, the Obama administration is signaling member nations they'll need to supply the forces.

The Chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, agreed with Secretary Gates telling reporters at the same off-camera briefing that he was "comfortable" with the timetable. Up to this point the U.S. Military has said only that it will begin to withdrawal troops starting in July, 2011, but had not given any indication of when most troops would be gone.

Secretary Gates was careful to say despite a large withdrawal by 2014, some troops and civilians will remain in Afghanistan for a long time. "We're going to remain a partner of Afghanistan even after our troops are gone," Gates said. "We walked away from Afghanistan in 1988, and we saw the consequences of that in 2001."

Secretary of State Hillary Clinton said some parts of the country are showing progress and could soon be protected by Afghan security forces. "This is a tough fight that we're in but we're convinced that starting next year there will be parts of Afghanistan that will be under control of the Afghan government and its security forces," Clinton said at a press conference in Australia with Gates on Monday.

It's well known that some of the northern provinces are experiencing less violence and that the real battle with the Taliban is happening in the south. Regions such as Kandahar and Helmand will be the most difficult to hand over.

AP contributed to this report.